This invention relates to protective coatings containing a chromogenic signal means, for general application to all surfaces, but with special significance when applied over lead-based paint surfaces and the like hazards.
The ingestion of lead-based paint has been widely recognized as a major pediatric disease, especially among young children ranging in age from about one to about five years. Childhood lead poisoning is a problem that faces the health departments and housing officials throughout the Nation. The ingestion of paint chips, crumbling plaster, cracking wallpaper, and the nibbling of windowsills, frames and banisters by young children have been recognized as the principal causes of lead poisoning. The National Bureau of Standards has estimated that more than 600,000 children in the United States have dangerous levels of lead in their blood.
This problem is particularly acute in large metropolitan areas having homes constructed prior to 1940. White lead was the commonly utilized white pigment in that era and was present in both the interior and the exterior paints that were used at that time. Moreover, inasmuch as lead-based paints were commercially available as recently as 1972, a portion of homes built or redecorated up to that time are likely to contain some lead-based paint.
While the actions of governmental agencies and the paint industry have now limited the commercial availability of paints containing significant quantities of lead, the problem of homes and other structures coated with lead-based paint still exists.
Lead poisoning can result in several well-known but non-specific clinical syndromes of illness in man, some of which include anemia, loss of appetite, insomnia, muscle and joint pains, severe abdominal pain (lead colic) and headaches. However, in children such symptoms of lead poisoning are often overlooked or are erroneously attributed to other diseases. As a result, the poisoning due to lead is not likely to be recognized until a late or rather severe stage. Severe cases of lead poisoning or recurrent uncontrolled exposure to lead is responsible for progressive renal insufficiency and cerebral incompetency. Central nervous system effects have also been observed and in some cases, death.
The diagnostic tests for detecting lead poisoning are the measurement of blood lead concentration, spontaneous urinary lead excretion, and the Edathamil calcium disodium (CaEDTA) Mobilization Test, but by the time these are used on a child or are able to pick up the excessive lead concentration, some damaging injury may have already occurred.
In spite of the efforts made by municipal organizations to detect and treat the lead poisoning problem in young children it is believed that high percentages of cases go undetected. Control of the ingestion of lead-based paint is not only a desirable program but also is a necessary effort for minimizing the exposure of children to this hazard. To this end the National Paint and Coatings Association has prepared a considerable amount of material with a view toward educating the public in the prevention of lead poisoning. Their principal message has been to sweep up old, flaking paint chips or plaster from the wall and off the floor, and to provide the child with something safe to chew on. If the child is seen eating paint chips, the supervising adult is advised to take the child to the doctor, clinic or public health department immediately for appropriate treatment. While this is important advice, it is not sufficient for cases where children are unsupervised or not adequately minded.
Of course, the most effective method of preventing the ingestion of lead-based paints by a child would be to remove the paint from the wall. However, because of the age of the structures, the multiple number of paint coatings placed on top of the lead-based paint, as well as the difficulty and cost involved in lead-based paint removal, this method is generally considered inadequate. Also, removal of the coating by heating, sanding and scraping techniques imposes hazards of exposure to the workers involved in the paint removal program.
Other methods to abate the hazard of lead-based paint fall into the general category of covering up the hazardous surface with another, relatively permanent, barrier material. Wall structures can be covered with gypsum board or plywood, or other rigid covering materials. Windowsills, frames, banisters and railings can be covered with more flexible materials such as fabric, canvas or flexible membranes; however, such methods in many cases are costly and impractical.
The inclusion of a bad tasting substance, i.e., an acerbic agent, in a paint has also be reported in literature as a feasible approach toward solving the lead-based paint ingestion problem. It has been postulated that the bad taste of the covering paint will discourage the child from eating paint chips; however, evidence available to date has not shown that this particular approach provides an effective solution to the problem. Apparently, bad taste alone will not adequately discourage a small child.
It has also been proposed to cover lead-based paint with coatings containing emetics. While emetics may be effective, such a proposal appears to be of limited acceptability because of physical and/or psychological reasons. Moreover, the child may tolerate a small dose of emetic on a daily basis, or its effect may be ignored.
The use of chelating agents for the control of lead poisoning also has been reported. Edathamil calcium disodium (CaEDTA), 2,3-dimercapto-1-propanol (BAL) and d-penicillamine have been evaluated as therapeutic agents for this purpose. However, the oral administration of CaEDTA to acutely ill patients has been reported to be ineffectual and potentially harmful. Thus, the inclusion of chelating agents into a coating which would be used as a covering for lead-based paints has to be approached with considerable caution.
All of the heretofore proposed methods thus appear to have some major deficiency.
On the other hand, the present invention provides a completely different approach, namely, a signal indicating the ingestion of an undesirable substance which the parent or supervising adult cannot overlook. Thus, for example, the presently contemplated protective coatings can provide an early indication or signal that an individual may have ingested lead-based paint or a similar undesirable substance. As a result of this signal, appropriate prophylactic measures can be taken before the onset of poisoning symptoms. In addition, the present invention contemplates a hazard abatement method utilizing paint which would be applied during the normal course of renovation or redecoration utilizing conventional applicators and techniques. This is an inexpensive and practical procedure which can be followed by any family living in an older house which is suspected of having been painted with a lead-based paint.